Heat treating furnace



April Y16, 1935. E. G. DE coRloLls ET A1. 1,997,630.

HEAT TREATING FURNACE Filed oct. 9, 19:51

F/G. l- /NvENToRs:

EG. DECOR/ous ATTORNEY Patented Apr.. 16, 1935 UNITED STATES PATENT Y 1,997,680 HEAT TREATNG FURNACE York Application October 9, 1931, Serial No. 567,910

8 Claims.

This invention relates to heat-treating furnaces of the type commonly employed for heat treating tools and the like and has for its object to provide improved ways and means for pre- 5 venting the inflow ofl air to the heat-treating chamber.

Referring to the drawing wherein the preferred form of the invention is shown,

Fig. 1 is a vertical longitudinal section through a munie furnace embodying the invention;

Fig. 2 is a vertical transverse section of the furnace on line 2 2 of Fig. l;

Fig. 3 is a horizontal cross section on line 3-3 of Fig. l, and

Fig. 4 is a horizontal section on line 4-61 of Fig. l, the View showing a slight modification of certain details.

The furnace comprises a chambered refractory structure F wherein is a mufe which is generally indicated at M, and which comprises a door or hearth 6, side walls 1, a roof B and an end wall 9, one end of the mule being open, the

muie being of refractory material.

The mufe M projects into the chamber of the structure F from one end wall II thereof, and is supported above the floor I2 of said chamber by a pair of laterally spaced supports I3 which preferably extend between the front and rear walls Il and I4, respectively, of the said chamber. A slab I5 is disposed across the supports I3 between the end wall 9 of -the mule and the adjacent wall I4 of the said chamber. It will, therefore, be seen that there is formed a compartment or chamber P below the mule, the supports I3 forming the side wall of the cornpartment. y

Firing into the compartment P through the rear end wall I4 of the furnace is a gas burner B of a type adapted to burn preformed mixtures of air and gas, the mixture being supplied under pressure from a suitable source of supply. As shown, the burner comprises a nozzle I6 set to discharge into an expansion combustion chamber I6', the burner as a whole being removably positioned in the furnace wall. Burners of this type are well known in the art. Similar burners B re into the upper portion of the furnace chamber and the spent gases from the burners B leave the furnace chamber through a suitable port or ports I'I in communication with an exhaust flue I8 formed in the wall structure of the furnace. The burners B' are the main heating burners for the mufe as will be readily appreciated.

While the burner B which fires into the compartment P serves to heat the floor of the mufe its primary function is to provide gaseous products of combustion for excluding air from the mule. Said products of combustion leave the compartment P by way of an elongated port or slot 2l! at the front or entrance end of the rnuiile M, the front wall II of the furnace chamber being recessed for that purpose. In other words, the compartment P may be said to extend to a point in advance of the terminal end 2I of the mule floor whereby to provide the port 20, the port beingv coextensive in length with the width of the muie and being relatively restricted in width. The combustion gases from the compartment P will therefore flow upwardly through the port 2li and form, as it were, a gaseous curtain in front of the mule.

It will be noted that the burner B discharges in a direction toward the port 20 and consequently, even in the absence of the compartment side walls I3, the gases from the burner B would l tend to flow towards and exhaust from the port 20 rather than through the exhaust port I'I. Moreover, in the absence of the side walls I3 it would merely be necessary to restrict the outlet from the flue I8 to such degree that combustion gases from the burner B (or from the burners B in the absence of the burner B) would flow through the port 20, it being noted that except for the ports II and 20 the furnace chamber surrounding the mufle is closed. However, inasmuch as means must be provided for spacing the muffle oor from the furnace chamber oor, it is preferred to make the Asupporting means I3 continuous as' shown. As shown in Fig. 4, the means I3 may terminate short of the front wall II of the furnace to provide side ports 22 for the escape of gas from the compartment P, the effective discharge area of the ports being controlled by movable dampers 23 adapted to be adjusted as by rods 28 extending outside of the furnace. The volume of gases flowing through the port 20 from the burner B may therefore be regulated as desired. It will also be understood that by regulating the proportions of air and gas in the'mixture supplied to the burner B the character of the combustion gases and hence ythe atmosphere in the munie can be controlled as desired, it being understood that some of the gases owing from the port 20 will enter the mule especially when the furnace is provided with a door 24 posir tioned as shown.

It is preferred to provide a door in front of the muftle, the door being arranged to be moved vertically. The door is recessed on its muie side to provide an upright channel 25 wherethrough the gases coming from the port 20 may flow upwardly and out to the atmosphere. It will be noted that the furnace wall adjacent the top of the door cooperates with the door to form a relatively restricted outlet 26. A pressure above that of the atmosphere will therefore tend to prevail in front of the munie and hence the entry of air into the mullle is effectively prevented. There may be provided a vent 2l from the muffle to insure circulation of gases within the muiiie especially when the door 24 is closed. This vent may also serve for the introduction of a pyrometer into the muille.

What is claimed is:-

1. In combination, a furnace chamber, a muffle extending into said chamber, a door spaced from the entrance to the mufe, and means for directing gases from within said chamber upwardly along the mutile side of the door in front of the entrance to the muiile.

2. In combination, a muille open at one end, means cooperating with the muie to form a closed chamber underneath the mule, a burner firing into said chamber, and an outlet from said chamber, said outlet comprising a relatively restricted passage extending transversely across the bottom of the muille immediately in front of the entrance thereto whereby gases from said chamber will discharge across said entrance.

3. In combination, a mume open at one end, means cooperating with the muille to forni a chamber therebelow, means for introducing gases under pressure into said chamber, a relatively restricted elongated outlet from said chamber positioned to discharge across the entrance to the munie, an exhaust passage independent of said outlet, and means for regulating the flow of gases from said chamber to said exhaust passage.

4. In combination, a muiile open at one end, a furnace surrounding the munie, means dividing the space about the munie into upper and lower compartments, an exhaust passage from the upper compartment, an outlet from the lower compartment ananged to discharge upwardly across the entrance to said munie, means for supplying heating gases to the respective compartments,

and means for regulating the degree of communication between said compartments.

5. In combination, a furnace chamber, a muiiie in said chamber, a slot substantially as long as the muffle is wide immediately in front of the entrance to the muflle whereby gases from the furnace may ow upwardly in front of said entrance, and a door disposed in front of said entrance, said door being provided with a vertically extending recess in its mume side to form a passage through which gases may flow away from said entrance.

6. A heat treating furnace comprising in combination, aA heating chamber, a passageway at the front communicating with the heating chamber, a combustion chamber separate from the heating chamber but positioned so that the heat of combustion is transmitted to the said heating chamber, and a duct communicating with the combustion chamber and terminating in a narrow transverse slot extending entirely across the said passageway, the said duct serving to conduct the hot gases of combustion from the combustion chamber to the passageway so as to form a inf-ving gaseous curtain `at the front of the heating chamber.

7. A furnace as set forth in claim 6, wherein the slot is at the bottom of the passageway and the gases move upward therefrom.

8. The combination in a heat treating furnace, of a heating chamber, a passageway at the front communicating with the heating chamber, a combustion chamber separate from the heating chamber but positioned so that the heat of combustion is transmitted to the said heating chamber, and a duct communicating with the combustion chamber and terminating in a narrow transverse slot extending across the bottom of the passageway so as to form a curtain of upward moving gases at the front of the heating chamber, a recess being formed at the top of the passageway above the duct for receiving the said upward moving gases.

ERNEST G. DE CORIOLIS. HENRY W. SCHRAMM. 

